Functionalized  main chain polymers

ABSTRACT

A non crosslinked, covalently crosslinked and/or ionically crosslinked polymer, having repeating units of the general formula (1) 
       —K—R—  (1)
 
     In which K is a bond, oxygen, sulfur, 
     
       
         
         
             
             
         
       
     
     the radical R is a divalent radical of an aromatic or heteroaromatic compound.

Functionalized fluorine free main chain polymers, like sulfonated polyaryl etherketones and polyethersulfones have been developed by thecompany Dupont in the past as an alternative to fluorinated cationexchanger like Nafion. Such polymer processed to membranes find use inmembrane processes, particularly in hydrogen fuel cells. Onedistinguishes at least two types of PEM hydrogen fuel cells(PolymerElectrolyteMembrane hydrogen fuel cells). The former converthydrogen and the latter methanol. In direct methanol fuel cells (DMFC)higher requirements are made to the membranes, than in hydrogen fuelcells which are operated exclusively with hydrogen at.

Ionically crosslinked membranes were developed by Kerres et al. Theseare acid base polymer blends and polymer (blend) membranes. An advantageof the ionically crosslinked acid base blend membranes is the higherflexibility of the ionic bonds and that these polymer/membranes do notdry so easily out at higher temperatures and in consequence do notbecome brittle so fast either. The ionic bindings show, however, thedisadvantage that they start at temperatures above 60 degrees Celsius toopen themselves what leads to a strong swelling up to the dissolving ofthe membrane.

In earlier applications was suggested to enclose a sulfonatedengineering main chain polymer into a covalent network of a secondpolymer. This procedure leads to technically applicable membranes forthe hydrogen hydrogen fuel cell, however, has the disadvantage in theDMFC that during the operation the danger of the bleeding out of thesulfonated component exists. So it was task to develop a polymer, thatbleeds out in aqueous or aqueous alcoholic surroundings little or not atall. Under “bleeding” you shall understand that a water-solublecomponent is dissolved.

Furthermore the polymer shall show a mechanical stability as good aspossible and an improved swelling behavior. The swelling behavior shallpreferably increase at a temperature of 90° C. in deionized water aroundless than 90% as compared to the control value at 30° C. related to theextension in the dimension (length, breadth, height).

A further object was to specify a crosslinked polymer which can be usedin fuel cells. The crosslinked polymer ought in particular to besuitable for use in fuel cells upward of 80° C., in particular upward of100° C. Membranes produced from the polymer shall particularly besuitable in direct methanol fuel cells.

Further disadvantage of the fluorine free polymeric cation exchanger,like sulfonated poly aryl etherketones and sulfonated polysulfones istheir lower acid strength in comparison with a polymeric fluorienatedsulfonic acid, such as Nafion of Dupont, which is considered as acomparison standard from the experts. The task was therefore provided tomake available a polymer with a higher acid strength than directly atthe main chain sulfonated polysulfone or directly at the main chainsulfonated polyetheretherketone as PEEK or PEKEKK.

Furthermore it was task to provide a method for the production of thecrosslinked polymer, too, that permits to produce the desired polymer ina simple way.

DESCRIPTION

These and additional not explicit mentioned objects are achieved bymeans of a polymer according to the invention which is not crosslinked,covalently crosslinked and/or ionically crosslinked as described in thepatent claim 1. Meaningful variations of the polymer of the presentinvention and combinations from this are described in the subclaims.Processes for preparing the polymer of the present invention aredescribed in the process claims. The claims for the use of the polymerof the present invention follow afterwards.

As far as the polymer according to the invention is a polymer with aproton exchanging group, such as sulfonic acid, phosphonic acid and/orcarbonic acid, whose acid strength has been increased according to theinvention and the task, a covalent and/or ionic crosslinking is notmandatory.

The non crosslinked, covalently crosslinked and/or optionally ionicallycrosslinked polymer according to the invention, particularly covalentlycrosslinked and/or optionally ionically crosslinked polymers, comprisesrepeating units of the general formula (1)

-Q-R—  (1)

in which Q is a bond, oxygen, sulfur

the radical R is a divalent radical of an aromatic or heteroaromatic oraliphatic compound.

Furthermore the invention concerns polymers with fluorine in the mainchain, such as polyvinylidendifluoride (PVDF), poly(vinylfluoride) (PVF)and polychlorotrifluorethylene and Analoga, like Kel-F and Neoflon.These polymers are already known and are changed into polymers of thepresent invention.

The polymers of the present invention get accessible by one or severalmodification steps of the starting polymer of the general formula (1).Polymers with repeating units of the general formula (1) are alreadyknown. They include, for example, polyarylenes, such as polyphenyleneand polypyrene, aromatic polyvinyl compounds, such as polystyrene andpolyvinylpyridine, polyphenylenevinylene, aromatic polyethers, such aspolyphenylene oxide, aromatic thioethers, such as polyphenylene sulfide,polysulfones, such as Radel R and Ultrason, and polyether ketones, suchas PEK, PEEK, PEKK and PEKEKK. Moreover, they also embrace polypyrroles,polythiophenes, polyazoles, such as polybenzimidazole, polyanilines,polyazulenes, polycarbazoles, polyindophenines, polyvinylidendifluoride(PVDF) and polychlorotrifluorethylene and analogues like Kel-F andNeoflon.

By one or more modifications with repeating units of the general formula(1) a polymer according to the invention is created with surprisingproperties.

By providing a polymer of the present invention, comprising repeatingunits of the general formula (1) is made available which isdistinguished in that (a) the radical R has at least in partsubstituents of the general formula (4J), (4K), (4L), (4M), (4N), (4O),(4P), (4Q) and/or (4R),

where the radicals R¹ independently of one another show the generalformula (888-1) or (888-2)

where M independently of one another is hydrogen, a one- or multivalentcation, preferably Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, TiO²⁺, ZrO²⁺, Ti⁴⁺, Zr⁴⁺,Ca²⁺, Mg²⁺ or an optionally alkylated ammonium is and X is a halogen oran optionally alkylated amino group, and where R², R³, R⁴, R³independently of one another is hydrogen, (4A), (4B), (4C), (4D), (4E),(4F), (4G), (4H), (4I), (4J), (4K), (4L), (4M), (4N), (4O), (4P), (4Q)and/or (4R) or a group having from 1 to 40 carbon atoms, preferably abranched or unbranched alkyl or cycloalkyl group or an optionallyalkylated aryl group or hetero aryl group is, which can be fluorinatedor partly fluorinated, it being possible for at least two of theradicals R², R³ and R⁴ to be closed to form an optionally aromatic ring,and/or the radical R¹ is a group of the general formula (5A), (5B),(5C), (5D), (5E), (5F), (5G) and/or (5H)

andb) the radical R has optionally bridges of the general formula (6A),(6B), and or (6C),

which join at least two radicals R to one another, Y being a grouphaving from 1 to 40 carbon atoms, preferably a branched or unbranchedalkyl or cycloalkyl group or an optionally alkylated aryl group, Z ishydroxyl, a group of the general formula (7)

or a group having a molecular weight of more than 14 g/mol composed ofthe optional components (5A), (5B), (5C), (5D), (5E), (5F), (5G), (5H),(4A), (4B), (4C), (4D), (4E), (4F), (4G), (4H), (4I), (4J), (4K), (4L),(4M), (4N), (4O), (4P), (4Q), (4R), H, C, O, N, S, P, halogen atoms, oneor multivalent cation and m is an integer greater than or equal to 2, itis possible in a manner which was not immediately foreseeable to makeavailable a polymer having improved properties, in particular formembrane applications, an improved swelling properties, a better protonconductivity and further defined adjustable functional groups for themost different technical applications.

At the same time the polymer of the invention and the crosslinkedpolymer of the invention display a number of further advantages.

These include, among others:

The doped polymer membranes have a low specific volume resistance,preferably less than or equal to 100 Ohm×cm at 20° C.

The doped polymer membranes possess only a low permeability forhydrogen, oxygen and methanol.

Also extremely thin membranes of the polymer of the invention, with atotal thickness of between 10 and 100 μm possess sufficiently goodmaterial properties at temperatures between 60° C. and 82° C. inparticular a very high mechanical stability and a low permeability forhydrogen, oxygen and methanol.

The doped polymer membrane is suitable for use in fuel cells upward of80° C., in some cases upward of 100° C. and in particular cases upwardof 110° C.

The doped polymer membrane is suitable for use in fuel cells upward of82° C., in particular under standard pressure.

The doped polymer membrane can be produced on an industrial scale.

In accordance with the present invention the polymer is covalentlyand/or ionically crosslinked. In accordance with the invention,crosslinked polymers are those polymers whose linear or branchedmacromolecules, which are of the same or different chemical identity andare present in the form of collectives, are linked to one another toform three-dimensional polymer networks. In this case the crosslinkingmay be effected both by way of the formation of covalent bonds and byway of the formation of ionic bonds.

The crosslinked polymer of the invention is preferably doped with acid.In the context of the present invention, doped polymers are thosepolymers which owing to the presence of doping agents exhibit anincreased proton conductivity in comparison with the undoped polymers.Dopants for the polymers of the invention are acids. Acids in thiscontext embrace all known Lewis and Brönsted acids, preferably inorganicLewis and Brönsted acids. Also possible is the use of polyacids,especially isopolyacids and heteropolyacids, and mixtures of differentacids. For the purposes of the present invention, heteropolyacids areinorganic polyacids having at least two different central atoms whichare formed as partial mixed anhydrides from in each case weak polybasicoxygen acids of a metal (preferably Cr, Mo, V, W) and of a nonmetal(preferably As, I, P, Se, Si, Te). They include, among others,12-molybdatophosphoric acid and 12-tungstophosphoric acid.

Dopants which are particularly preferred in accordance with theinvention are sulfuric acid and phosphoric acid. One especiallypreferred dopant is phosphoric acid (H₃PO₄).

Furthermore are particularly preferred the placement of zirkoniumphosphate and titan sulfate by methods of someone skilled in the art andfurthermore preferred are modified and nonmodified phyllosilicate ortectosilicate. With this modification method Montmorillonite isparticularly preferred, which is added during the membrane formingprocess. Methods for the production of doped plastic membranes areknown.

The doping agents are fixed by a calcination process in the membrane andtransferred into the strong Lewis acidic form. Particularly preferred isthe calcination of titan sulfate and zirconium phosphate in themembrane. Optionally the calcination is followed by anew doping and/orfurther doping. Preferred doping agents are again phosphoric acid,sulfuric acid and the above mentioned hetero polyacids. The procedurecan be repeated optionally severalfold.

A suitable calcination temperature is the temperature range of 60° C.until just below the decomposition temperature of the polymer to bedoped. This is above 300° C. for fluorinated polymers andpolybenzimidazole. Particularly preferred is the temperature range of100° C. to 300° C.

Some doping agents are fixed in the membrane for a time technicallyapplicable by the calcination.

The crosslinked polymer of the invention has repeating units of thegeneral formula (1), especially repeating units corresponding to thegeneral formulae (1A), (1B), (1C), (1D), (1E), (1F), (1G), (1H), (1I),(1T), (1K), (1L), (1M), (1N), (1O), (1P), (1Q), (1R), (1S) and/or (1T):

Independently of one another here the radicals R⁶ which are identical ordifferent, are 1,2-phenylene, 1,3-phenylene, 1,4-phenylene,4,4′-biphenyl, a divalent radical of a heteroaromatic, a divalentradical of a C₁₀ aromatic, a divalent radical of a C₁₄ aromatic and/or adivalent pyrene radical. An example of a C₁₀ aromatic is naphthalene; ofa C₁₄ aromatic, phenanthrene. The substitution pattern of the aromaticand/or heteroaromatic is arbitrary, in the case of phenylene, forexample, R⁶ may be ortho-, meta- and para-phenylene.

The radicals R⁷, R⁸ and R⁹ designate monovalent, tetravalent andtrivalent aromatic or heteroaromatic groups, respectively, and theradicals U, which are identical within a repeating unit, are an oxygenatom, a sulfur atom or an amino group which carries a hydrogen atom, agroup having 1-20 carbon atoms, preferably a branched or unbranchedalkyl or alkoxy group, or an aryl group as a further radical.

The polymers with repeating units of the general formula (1) that areparticularly preferred in the context of the present invention includehomopolymers and copolymers, examples being random copolymers, such asVictrex 720 P and Astrel. Especially preferred polymers are polyarylethers, polyaryl thioethers, polysulfones, polyether ketones,polypyrroles, polythiophenes, polyazoles, phenylenes,polyphenylenevinylenes, polyanilines, polyazulenes, polycarbazoles,polypyrenes, polyindophenines and polyvinylpyridines, especiallypolyaryl ethers:

Especially preferred in accordance with the invention are crosslinkedpolymers with repeating units of the general formula (1A-1), (1B-1),(1C-1), (1I-1), (1G-1), (1E-1), (1H-1), (1I-1), (1F-1), (1J-1), (1K-1),(1L-1), (1M-1) and/or (1N-1).

In the context of the present invention, n designates the number ofrepeating units along one macromolecule chain of the crosslinkedpolymer. This number of the repeating units of the general formula (1)along one macromolecule chain of the crosslinked polymer is preferablyan integer greater than or equal to 10, in particular greater than orequal to 100. The number of repeating units of the general formula (1A),(1B), (1C), (1D), (1E), (1F), (1G), (1H), (1I), (1J), (1K), (1L), (1M),(1N), (1O), (1P), (1Q), (1R), (1S) and/or (1T) along one macromoleculechain of the crosslinked polymer is preferably an integer greater thanor equal to 10, in particular greater than or equal to 100.

In one particularly preferred embodiment of the present invention, thenumerical average of the molecular weight of the macromolecule chain isgreater than 25,000 g/mol, appropriately greater than 50,000 g/mol, inparticular greater than 100,000 g/mol.

The crosslinked polymer of the invention may in principle also containdifferent repeating units along a macromolecule chain. Preferably,however, along one macromolecule chain it contains only identicalrepeating units of the general formula (1A), (1B), (1C), (1D), (1E),(1F), (1G), (1H), (1I), (1J), (1K), (1L), (1M), (1N), (1O), (1P), (1Q),(1R), (1S) and/or (1T).

In the context of the present invention the radical R has at least inpart substituents of the general formula (4A), (4B), (4C), (4D), (4E),(4F), (4G), (4H), (4I), (4J), (4K), (4L), (4M), (4N), (4O), (4P), (4Q)and/or (4R), preferably of the general formula (4A), (4B), (4C), (4D),(4J), (4K), (4L) and/or (4M), appropriately of the general formula (4A),(4B), (4C), (4J), (4K) and/or (4L), in particular of the general formula(4J) and/or (4K):

Here, the radicals R¹ independently of one another designate a bond or agroup having from 1 to 40 carbon atoms, preferably a branched orunbranched alkyl or cycloalkyl group or an optionally alkylated arylgroup, which optionally contain one or more fluorine atoms.

In the context of one especially preferred embodiment of the presentinvention, R1 is a methylene group (—CH₂—) and/or a partially orcompletely fluorinated methylene group (—CFH—) or (—CF₂—). Additionallyto the structure as defined in the previous sentence, R¹ designates in afurther especially preferred embodiment a bond. R¹ contains the formula(888-1) or (888-2).

M stands for hydrogen, a one or multi-valent metal cation, preferablyLi⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Zr⁴⁺, Ti⁴⁺, ZrO²⁺, or an optionally alkylatedammonium ion, appropriately for hydrogen or Li⁺, in particular forhydrogen.

X is a halogen or an optionally alkylated amino group.

Moreover, in accordance with the invention, the radical R has in partsubstituents of the general formula (5A), (5C), (5D), (5E), (5F), (5G),(5H) and/or (5B), preferably (5E),

and/or the radical R is in part a group of the general formula (5G)and/or (5H), preferably (5G).

In this context the radicals R², R³, R⁴ and R⁵ independently of oneanother denote a group having from 1 to 40 carbon atoms, preferably abranched or unbranched alkyl or cycloalkyl group or an optionallyalkylated aryl group, it being possible for at least two of the radicalsR², R³, R⁴ and R⁵ to be closed to form an optionally aromatic ring.

Particularly advantageous effects can be achieved if R has at least inpart substituents of the general formula (5A-1) and/or (5A-2).

Here, the radicals R¹⁰ denotes an optionally alkylated aryl group, whichcontains at least one optionally alkylated amino group, or an optionallyalkylated heteroaromatic, which either has at least one optionallyalkylated amino group or has at least one nitrogen atom in theheteroaromatic nucleus. R¹¹ is hydrogen, an alkyl, cycloalkyl, aryl orheteroaryl group or a radical R¹⁰ with the definition specified above,it being possible for R¹⁰ and R¹¹ to be identical or different.

Especially preferred in accordance with the invention are substituentsof the formula (5A-1) in which R¹⁰ is an optionally alkylated anilineradical or pyridine radical, preferably an alkylated aniline radical.Moreover, particular preference is also given to substituents of theformula (5A-2) in which R¹⁰ and R¹¹ are optionally alkylated anilineradicals or pyridine radicals, preferably alkylated aniline radicals.

In the context of the present invention the radical R can have in partbridges of the general formula (6),

which join at least two radicals R to one another, Y being a grouphaving 1 to 40 carbon atoms, preferably a branched or unbranched alkylor cycloalkyl group or optionally alkylated aryl group, appropriately alinear or branched alkyl group containing from 1 to 6 carbon atoms.Z designates hydroxyl, a group of the general formula

or a group having a molecular weight of more than 20 g/mol composed ofthe optional components H, C, O, N, S, P and halogen atoms, and m standsfor an integer greater than or equal to 2, preferably 2.

The polymer of the invention is preferably doped with acid. In thecontext of the present invention, doped polymers are those polymerswhich owing to the presence of doping agents exhibit an increased protonconductivity in comparison with the undoped polymers. Dopants for thepolymers of the invention are acids. Acids in this context embrace allknown Lewis and Brönsted acids, preferably inorganic Lewis and Brönstedacids. Also possible is the use of polyacids, especially isopolyacidsand heteropolyacids, and mixtures of different acids. For the purposesof the present invention, heteropolyacids are inorganic polyacids havingat least two different central atoms which are formed as partial mixedanhydrides from in each case weak polybasic oxygen acids of a metal(preferably Cr, Mo, V, W) and of a nonmetal (preferably As, I, P, Se,Si, Te). They include, among others, 12-molybdatophosphoric acid and12-tungstophosphoric acid.

Dopants which are particularly preferred in accordance with theinvention are sulfuric acid and phosphoric acid. One especiallypreferred dopant is phosphoric acid (H₃PO₄).

By way of the degree of doping it is possible to influence theconductivity of the polymer membrane of the invention. As theconcentration of dopant goes up, the conductivity increases until amaximum is reached. In accordance with the invention, the degree ofdoping is reported as mole acid per mole repeating unit of the polymer.In the context of the present invention a degree of doping of between 3and 15, in particular between 6 and 12, is preferred.

Processes for preparing doped polymer membrane are known. In onepreferred embodiment of the present invention they are obtained bywetting a polymer of the invention for an appropriate time, preferably0.5-96 hours, with particular preference 1-72 hours, at temperaturesbetween room temperature and 100° C. and, where appropriate, underelevated pressure with concentrated acid, preferably with highlyconcentrated phosphoric acid.

The spectrum of properties of the crosslinked polymer of the inventioncan be modified by varying its ion exchange capacity. The ion exchangecapacity lies preferably between 0.5 meq/g and 1.9 meq/g, based in eachcase on the total mass of the polymer.

The polymer of the invention has a low specific volume resistance,preferably of not more than 100 Ωcm, appropriately of not more than 50Ωcm, in particular of not more than 20 Ωcm, in each case at 25° C.

The properties of the polymer membrane of the invention may becontrolled in part by its total thickness. Nevertheless, even extremelythin polymer membranes possess very good mechanical properties andrelatively low permeability for hydrogen, oxygen, and methanol. They aretherefore suitable for use in fuel cells upward of 80° C., appropriatelyupward of 100° C., and in particular for use in fuel cells upward of120° C., without it being necessary to reinforce the edge region of themembrane electrode assembly. The total thickness of the doped polymermembrane of the invention is preferably between 50 and 100 μm,appropriately between 10 and 90 μm, in particular between 20 and 80 μm.

In the context of one especially preferred embodiment of the presentinvention it swells by less than 100% in deionised water at atemperature of 90° C.

Processes for preparing the crosslinked polymer of the invention areobvious to the person skilled in the art. Nevertheless, in the contextof the present invention a procedure which has proven especiallysuitable is that in which one or more precursor polymers whichindividually or in to contain the functional groups a), b) and d), d)designating sulfinate groups of the general formula (6)

is or are reacted with a compound of the general formula (7)

YL_(m)  (7)

where L is a leaving group, preferably an F, Cl, Br, I, tosylate, and nis an integer greater than or equal to 2, preferably 2. Each precursorpolymer preferably has repeating units of the general formula (1).Furthermore, appropriately, it is not covalently crosslinked. Where inat least one precursor polymer the radical R has at least in partsubstituents of the general formula (5A) or is at least in part a groupof the general formula (5C), the reaction with the compound (7) mayalso, moreover, lead to the formation of bridges of the general formula(8) and/or (9).

Also conceivable is the formation of bridges between differentsubstituents of the general formula (5A) and/or between different groupsof the general formula (5C).

In one particularly preferred embodiment of the present invention apolymer mixture is used comprising

1) at least one precursor polymer having functional groups a),

2) at least one precursor polymer having functional groups b), and

3) at least one precursor polymer having functional groups d).

In another particularly preferred embodiment of the present invention apolymer mixture is used comprising

1) at least one precursor polymer having functional groups a) and b) and

2) at least one precursor polymer having functional groups d).

In accordance with another particularly preferred embodiment of thepresent invention it may also be particular advantageous to use apolymer mixture comprising

1) at least one precursor polymer having functional groups a) and d) and

2) at least one precursor polymer having functional groups b).

Furthermore, processes wherein use is made of a polymer mixturecomprising

1) at least one precursor polymer having functional groups a) and

2) at least one precursor polymer having functional groups b) and d)also constitutes a particularly preferred embodiment of the presentinvention.

In accordance with the invention it may also be exceptionallyappropriate to use at least one polymer having functional groups of thegeneral formula a), b) and d).

The precursor polymer or polymers for use in accordance with theinvention may in principle have different repeating units of the generalformula (1). Preferably, however, they have only identical repeatingunits of the general formula (1A), (1B), (1C), (1D), (1E), (1F), (1G),(1H), (1I), (1J), (1K), (1L), (1M), (1N), (1O), (1P), 1Q), (1R), (1S)and/or (1T).

The number of repeating units of the general formula (1A), (1B), (1C)(1D), (1E), (1F), (1G) (1H), (1I), (11J), (1K), (1L), (1M), (1N), (1O),(1P), (1Q) (1R), (1S) and/or (1T) is preferably an integer greater thanor equal to 10, preferably at least 100 repeating units.

In one particularly preferred embodiment of the present invention thenumerical average of the molecular weight of the precursor polymer orpolymers is greater than 25,000 g/mol, appropriately greater than 50,000g/mol, in particular greater than 100,000 g/mol.

The synthesis of the precursor polymers having functional groups of thegeneral formula a), b) and/or d) is already known. It can take place,for example, by reacting a polymer of the general formula (1) withn-butyllithium in a dried aprotic solvent, preferably tetrahydrofuran(THF), under an inert gas atmosphere, preferably argon, and solithiating it.

In order to introduce the functional groups, the lithiated polymer is[lacuna] in a manner known per se with suitable functionalizing agents,preferably with alkylating agent of the general formula

L-Subst.  (10)

where Subst. is the substituent to be introduced; with ketones and/oraldehydes, which are reacted to the corresponding alkoxides; and/or withcarboxylic esters and/or carbonyl halides, which are reacted to thecorresponding ketones. The introduction of sulfonate groups may also beeffected by reacting the lithiated polymer with SO₃, and theintroduction of sulfinate groups by reacting the lithiated polymer withSO₂.

Through successive reaction with two or more different functionalizingagents, polymers are obtained which have at least two differentsubstituents.

For further details, refer to the state of the art, in particular to thedocuments U.S. Pat. No. 4,833,219, J. Kerres, W. Cui, S. Reichle; Newsulfonated engineering polymers via the metalation route. 1. “Sulfonatedpoly-(ethersulfone) PSU Udel via metalation-sulfination-oxidation” J.Polym. Sci.: Part A: Polym. Chem. 34, 2421-2438 (1996), WO 00/09588 A1,whose disclosure content is hereby explicitly incorporated by reference.

The degree of functionalization of the precursor polymers liespreferably in the range from 0.1 to 3 groups per repeating unit,preferably between 0.2 and 2.2 groups per repeating unit. Particularpreference is given to precursor polymers having from 0.2 to 0.8 groupsa), preferably sulfonate groups, per repeating unit. Moreover, precursorpolymers having from 0.8 to 2.2 groups b) per repeating unit have beenfound particularly appropriate. Moreover, particularly advantageousresults are achieved with precursor polymers which have from 0.8 to 1.3groups d) per repeating unit.

In the context of the present invention it has proven especiallyappropriate to dissolve the precursor polymer or polymers in adipolar-aprotic solvent, preferably in N,N-dimethylformamide,N,N-dimethyl-acetamide, N-methylpyrrolidone, dimethyl sulfoxide orsulfolane, and to react the solution with the halogen compound, withstirring.

Particularly advantageous results can be achieved here if

a) the polymer solution is spread as a film on a substrate, preferablyon a glass plate or a woven or nonwoven fabric, and

b) the solvent is evaporated, where appropriate at an elevatedtemperature of more than 25° C.

c) and/or under a reduced pressure of less than 1000 mbar, to give apolymer membrane.

The properties of the polymer of the invention may also be enhanced by

a) treating the polymer in a first step with an acid and

b) treating the polymer in a further step with deionised water, thepolymer being treated where appropriate with an aqueous alkali prior tothe first step.

Possible fields of use for the polymer of the invention are evident tothe skilled worker. It is particularly suitable for all applicationswhich are indicated for crosslinked polymers having low specific volumeresistances, preferably less than 100 Ωcm at 25° C. On the basis oftheir characteristic properties, they are suitable in particular forapplications in electrochemical cells, preferably in secondarybatteries, electrolysis cells, and in polymer electrolyte membrane fuelcells, especially in hydrogen fuel cells and direct methanol fuel cells.

Moreover, they may also be employed to particular advantage in membraneseparation operations, preferably in the context of gas separation,pervaporation, perstraction, reverse osmosis, nanofiltration,electrodialysis, and diffusion dialysis.

The invention is illustrated in more detail below using examples andcomparative examples, without any intention that the teaching of theinvention should be restricted to these examples. The property valuesreported, like the values described above, were determined as follows:

In order to determine the ion exchange capacity, IEC, a piece ofprotonated ionomer membrane was dried to constant weight. 1 mg of themembrane was introduced into about 50 ml of saturated NaCl solution. Asa result, there was ion exchange of the sulfonate groups, with the Hions passing into the saturated solution. The solution with the membranewas shaken or stirred for about 24 hours. Thereafter, 2 drops of theindicator bromothymol blue were added to the solution, which wastitrated with 0.1-normal NaOH solution until the change of color fromyellow to blue. The IEC was calculated as follows:

IEC[meq/g]=(normality of NaOH[meq/ml]*consumption of NaOH[ml]*factor ofNaOH)/mass of membrane[g].

The specific volume resistance R^(sp) of the membranes was determined bymeans of impedance spectroscopy (IM6 impedance meter, Zahner elektrik)in a Plexiglas unit with gold-coated copper electrodes (electrode area0.25 cm²). Here, in accordance with the invention, the impedance atwhich the phase angle between current strength and voltage was 0designates the specific volume resistance. The actual measurementconditions were as follows: 0.5 N HCl was used, the membrane undermeasurement was packed between two Nation 117 membranes, and themultilayer arrangement of Nafion 117/membrane/Nafion 117 membrane waspressed between the two electrodes. In this way, the interfacialresistances between membrane and electrode were eliminated by measuringfirst of all the multilayer arrangement of all three membranes and thenthe two Nafion 117 membranes alone. The impedance of the Nafionmembranes was substrated from the impedance of all three membranes. Inthe context of the present invention the specific volume resistanceswere determined at 25° C.

In order to determine the swelling, the membranes were equilibrated indeionised water at the respective temperature and then weighed(=m^(swollen)). The membranes were then dried at elevated temperature ina drying oven and weighed again (=m^(dry)). The degree of swelling iscalculated as follows:

Q=m ^(swollen) −m ^(dry))/m ^(dry)

a) polymers useda-1) PSU Udel

PSU P 1800 (Amoco)

a-2) PEK-SO₃Li:Lithium salt of sulfonated polyether ketone PEK

Preparation:

100 g of PEK-SO₃H having an ion exchange capacity of 1.8 meq SO₃H/gpolymer were stirred for 24 hours in 1000 ml of a 10% strength by weightaqueous LiOH solution. Thereafter the Li-exchanged PEK-SO₃Li wasfiltered off, washed with water until the wash water gave a neutralreaction, and then dried at 100° C. for 48 h. The resulting polymercontained 0.4 SO₃Li units per repeating unit (ion exchange capacity(IEC) of the protonated form=1.8 meq SO₃H/g).

a-3) PSU-SO₂Li:

Lithium salt of sulfinated polyether sulfone PSU Udel

obtained in accordance with U.S. Pat. No. 4,833,219 or J. Kerres, W.Cui, S. Reichle; New sulfonated engineering polymers via the metalationroute. 1. “Sulfonated poly(ethersulfone) PSU Udel viametalation-sulfination-oxidation” J. Polym. Sci.: Part A: Polym. Chem.34, 2421-2438 (1996) IEC of the protonated form=1.95 meq SO₂Li/ga-4) PSU-DPK:

obtained by reacting 2,2′-dipyridyl ketone with lithiated PSU Udel (inaccordance with WO 00/09588 A1);one 2,2′-dipryidyl ketone unit per repeating unita-5) a-5) Synthesis of PSU-P3-SO₂Li, PSU-EBD-SO₂Li,

PSU-P3-SO₂Li,

First of all PSU Udel was dissolved in dry THF and the solution wascooled to −75° C. under argon. Traces of water in the reaction mixturewere removed with 2.5 M n-butyllithium (n-BuLi). The dissolved polymerwas subsequently lithiated with 10 M n-BuLi. The batch was left to reactfor one hour and then pyridine-3-aldehyde or4,4′-bis(N,N-diethylamino)benzo-phenone was added. The reactiontemperature was thereafter raised to −20° C. for one hour. For thereaction with SO₂ it was subsequently cooled again to −75° C. and theSO₂ was passed in.

For working up, 10 ml of an isopropanol/water mixture was introduced bysyringe into the reaction solution, which was heated to roomtemperature, and the polymer was precipitated in an excess ofisopropanol, and the resulting polymer was filtered off and washed,where appropriate with isopropanol. For purification, the polymer wassuspended in methanol and filtered off again. The polymer was dried invacuo, preferably at 80° C. The degrees of substitution were obtained byquantitative evaluation of the ¹H-NMR spectra.

TABLE 1 Synthesis of PSU-P3-SO₂Li and PSU-EBD-SO₂Li Substitutionsgradpro Ansatz Wiederholungseinheit PSU-P3-SO₂Li 10 ml 10M BuLi 0.8Pyridin-3-aldehyd 1000 ml THF 1.2 SO₂Li 22.1 g PSU Udel ® 5.35 gPyridin-3-aldehyd SO₂ PSU-DEB- 10 ml 10M BuLi 0.4 4,4-Bis(N,N- SO₂Li1000 ml THF diethylamino)benzophenon 22.1 g PSU Udel ® 1.6 SO₂Li 16.22 g4,4′-Bis-(N,N- diethylamino)benzophenon SO₂

b.) Membrane Production

The polymers PEK-SO₃Li, PSU-P3-SO₂Li, PSU-EBD-SO₂Li, PSU-DPK and/orPSUSO₂Li were dissolved in NMP in accordance with Table 2 and filtered.The polymer solution was then degassed in vacuo and subsequently admixedwith 1,4-diiodobutane. It was subsequently poured onto a glass plate anddrawn but using a doctor blade. The glass plate was dried in an oven at60° C. for 1 hour, then at 90° C. for a further hour and finally at 120°C. under vacuum overnight. The plate was cooled to room temperature andplaced in a waterbath. The membrane was separated from the glass plateand stored in 10% HCl in an oven at 90° C. for one day. It wassubsequently conditioned in deionised water at 60° C.

The polymer of the present invention as described so far as well as allpossible combinations is characterised in that it has at least onesubstituent of the general formula (4J), (4K), (4L), (4M), (4N), (4O),(4P), (4Q) and/or (4R). If it has not a substituent of the groupmentioned above, than it sows at least a substituent of the generalformula (5C), (5D), (5G), (5H) or that it is crosslinked by acrosslinking bridge of the general formula (6B) and/or (6C).

Particularly preferred is the presence of substituent (2J) and/or (2K).

Polymer-(2J) Polymer-(2K)

Surprisingly, it has been shown that the acid strength of a protonexchanging acid, especially of sulfonic acid and phosphoric acid, isincreased in the presence of a sulfo group at the carbon atom bearingthe proton exchanging group.

Subsequent figures illustrate the structures:

-   -   

In the examples is R=polymer substituent

According to the present invention are also polymers which start onlyfrom sulfinated polymers of the general formula (1) and where thesulfinate groups are transformed in subsequent reactions in sulfonicgroups which are crosslinked partly or completely by a carbon containingradical with a further sulfinated polymer. The carbon containing radicalR carries the functional groups. These can be acids or/and bases.

The polymers of the present invention and the membranes produced fromthese are suited for the production of membrane electrode arrays. Theelectrodes applied on the membrane, e.g. in form of a paste, ink or by apowder coating method, can be crosslinked covalently by alkylatingcrosslinker with reactive groups to the membrane. The membrane as wellas the applied electrodes contain before the reaction not yet reactedsulfinic acid groups, especially preferred are sulfinates. If di- oroligo halogeno crosslinker, which if necessary contain functional groups(4A) to (4R), are added to the electrode paste containing precursor ofpolymeric cation exchanger as well as polymeric sulfinates, then thepolymeric sulfinates of the electrode paste react with the freepolymeric sulfinates of the membrane. The resulting covalent crosslinksolves an existing problem in the lacking bonding of the electrodes tothe membrane.

Possible fields of use for the polymer of the invention and covalentlycrosslinked and/or ionically crosslinked polymer of the invention areevident to the skilled worker. It is particularly suitable for allapplications which are indicated for crosslinked polymers, especiallywith ion conductance. Particularly suitable for applications inelectrochemical cells, preferably in secondary batteries, electrolysiscells, and in polymer electrolyte membrane fuel cells, especially inhydrogen fuel cells and direct methanol fuel cells.

Moreover, the polymers of the present invention may be employed in othermembrane separation operations, preferably in gas separation,pervaporation, perstraction, reverse osmosis, nanofiltration,electrodialysis, perstraction and diffusion dialysis.

The invention is illustrated below using examples, without any intentionthat the teaching of the invention should be restricted to theseexamples.

The new polymers can be prepared by different methods.

As an example the route via a polymeric sulfinic acid is shown.Polymeric sulfinic acids are accessible among others by preparationsdescribed by Guiver et al. and also by Kerres et al. The polymericsulfinic acid salt reacts with a mono or oligo halide bearing at least afurther functional group (4A) to (4I) compound by elimination of Lihalide and sulfur alkylation or sulfurarylation. The halide compoundcontains preferably the halides fluorine, chlorine, bromine and/oriodine as cleavable anion. Iodine is eliminated already at roomtemperature (25° C.), bromine at temperatures over 30° C. and chlorineis eliminated only under drastic conditions. Fluorine is a leaving groupif the fluorine atom is connected to an aryl group or an hetero arylgroup, a simple example is p-fluorine benzene sulfonate.

The remaining radical e.g. (4A) to (4I) carries now the desiredfunctional group. By the neighbouring sulfonic group the acid strengthis increased considerably. Between the sulfonic group and the protonexchanging group, e.g. sulfonic acid, is at least one carbon atom,preferred are the methylene group —CH2- and the ethylene group—CH2-CH2-. The increase in acid strength is with up to two carbon atomsin direct line to the proton exchanging group clearly detectable.Membranes made from the polymer of the invention show a better protonconductivity compared to identical polymers with the proton exchanginggroup directly connected to the aromatic ring. If one of theneighbouring hydrogen atoms is additionally replaced with fluorine thereis a further increase in acid strength.

Subsequently is the preparation of a sulfonic acid which acid strengthis strongly increased by the neighbouring group —SO₂—CH₂—.

Sulfinated polysulfone PSU-SO₂—Li is prepared as described as undera-3). The IEC of the protonated form is 1.95 meq SO₂Li/g. It isdissolved in NMP and then an equivalent amount of the sodium salt ofbromine methane sulfonate is added. After heating ne obtains thefollowing compound dissolved in NMP PSU-SO₂—CH₂—SO₃ ⁻Na⁺ with an IEC of1.95 meq SO₃Li/g.

Instead of bromine methane sulfonate bromine ethane sulfonate (sodiumsalt) is reacted in the next example with PSU-SO₂—Li. The reaction issuccessful and after evaporation of the solvent and recrystallizationthe pure compound PSU-SO₂—CH₂CH₂—SO₃ ⁻Na⁺ is obtained. If in the lastexample not the equivalent amount of bromine ethane sulfonate (sodiumsalt) is added but only half, PSU-SO₂—CH₂CH₂—SO₃ ⁻—Na⁺ with an IEC of0.9 meq SO₃Li/g is obtained and an IEC of 1.0 meq SO₂Li/g remains in thesame molecule. The solvent is evaporated in the drying oven at atemperature of appr. 80° C. until the solution has a concentration ofappr. 10-15% weight. Then it is cooled to room temperature (25° C.) andan equivalent amount of diiodine butane is added. The amount of diiodinebutane is calculated based on the crosslinking of the free sulfinategroups. The solution is then processed to a membrane on a glass plateand the remaining solvent NMP is evaporated in the drying oven.Acovalent crosslinked membrane is obtained which proton exchanging grouphas a considerably bigger acid strength as the control. Also theoxidation of the excess sulfinate groups to sulfonic acid groups iseconomised as it should be done in the control. The proton conductivityof the membrane with PSU-SO₂—CH₂CH₂—SO₃H is 20% lower as in the control,which has only PSU-SO₃H as proton exchanging group.

A considerable increase in the stability of the membrane has beenrealized using PEEK-SO—Li with an IEC of 2.3 meq SO₂Li/g. Followingfigure explains the reaction:

The membrane is transformed by posttreatment in aqueous mineral acid andwater in the acid form. Additionally the formed salts are removed. Thefollowing figure explains one embodiment of the polymer of theinvention.

R30 is (4A), (4B), (4C), (4F), (4G), (4H) and/or

where H at the nitrogen can be substituted by an aryl- or alkyl group.R¹ can contain additionally a functional group from (4A) to (4R), and agroup from (5A) to (5H).

In a further especially preferred embodiment polymers are prepared,which display one of the following groups:

where P is a polymer as described on pages 9 to 16. R¹ is defined as inthe description of R¹ for the substituents (4A), (4B), (4C), (4D), (4F),(4G), (4H), (4I), (4J), (4K), (4L), (4M), (4N), (4O), (4P), (4Q) or(4R). R55 is one of the substituents from (4A), (4B), (4C), (4D), (4F),(4G), (4H), (4I), (4J), (4K), (4L), (4M), (4N), (4O), (4P), (4Q) or(4R).

Furthermore are preferred polymers which shows one of the followinggroups

where P is a polymer as described on pages 9 to 16. R¹ is defined as inthe description of R¹ for the substituents (4A), (4B), (4C), (4D), (4F),(4G), (4H), (4I), (4J), (4K), (4L), (4M), (4N), (4O), (4P), (4Q) or(4R). R55 is one of the substituents from (4A), (4B), (4C), (4D), (4F),(4G), (4H), (4I), (4J), (4K), (4L), (4M), (4N), (4O), (4P), (4Q) or(4R).

In the following further routes are disclosed to the person skilled inthe art to prepare at least one of the groups (15-1), (15-2), (15-3),(15-4), (15-5) or (15-6).

After Guiver et al. or Kerres et al. and an application not yetpublished polymeric sulfinic acids are state of the art. A polymericsulfinic acid is alkylated after the general formula

To this e.g. sulfinated polysulfone is dissolved in NMP and mixed withan equivalent amount of iodine etane carbonic acid. Already after slightheating lithium iodide is eliminated and the corresponding sulfone withan endstanding carboxyl group is formed.

PSU-SO₂Li+J-CH₂—COOH→PSU-SO₂—CH₂—COOH+LiJ

Another example is sulfinated PEEK or PEK or PEKEKK or PEEKK.

PEEK-SO₂Li+J-CH₂—COOH→PEEK-SO₂—CH₂—COOH+LiJ

A further route:

Polysulfone is metallated according to prior art with butyl lithium at−60° C. as described by e.g. Guiver. Then an equivalent amount of methyliodide is added. One let rise to −10° C. in order to completelymethylate the polysulfone. The methylated polysulfone is cooled downagain to −60° C. and the equivalent amount of butyl lithium is added tothe metallation. Then the equivalent amount of one molecule SO₂Cl₂ perat least more than once metallated methyl group is added and then iodinedissolved in THF is injected. The preparation is described in detail inthe patent application DE 3636854 A1. The resulting polymer isfluorinated by the generally known Finkelstein reaction and is freedfrom solvent. The polymer is then hydrolyzed in water, acid and/or baseand the sulfonic acid is liberated.

PSU-Li+CH₃J→PSU-CH₃+LiJ

PSU-CH₃ is e.g.

Further route:

Further route:

Further route:

The polymeric sulfinic acids (P—SO₂Li) P=polymer can react as anucleophil with:

in which R can be taken from R¹.Further alkylating agents are:

R can independently from each other be taken from R¹.

What is claimed is:
 1. A non-crosslinked, covalently cross-linked and/orionically cross-linked polymer, having repeating units of the generalformula (1)—K—R—  (1) in which K is a bond, oxygen, sulphur,

the radical R is a divalent radical of an aromatic or heteroaromaticcompound, wherein a) the radical R has at least in part substituents ofthe general formula (21), (2K), (4L), (4M), (4N), (40), (4P), (4Q),or(4R),

where the radicals R¹ independently of one another are a bond or a grouphaving 1 to 40 carbon atoms, preferably a branched or unbranched alkylor cycloaikyl group or an optionally alkylated aryl group, M ishydrogen, a metal cation, preferably Li³⁰ , Na⁺, K⁺, Rb⁺, Cs⁺, TiO²⁺,ZrO², or an optionally alkylated ammonium ion, and X is a halogen or anoptionally alkylated amino group, b) the radical R has at least in partsubstituents of the general formula (5E) and/or (5F)

in which R², R³, R⁴ and R⁵ independently of one another are hydrogen, agroup having from 1 to 40 carbon atoms, preferably a branched orunbranched alkyl or cycloalkyl group or an optionally alkylated arylgroup, it being possible for at least two of the radicals R², R³ and R⁴to be closed to form an optionally aromatic nng, and or the radical R isat least in part a group of the general formula (5C) and/or (5D)